(a) Field of the Invention
The present invention relates generally to a liquid crystal display (LCD) and, more particularly, to a display panel used for a transflective LCD and a method of manufacturing the same.
(b) Description of the Related Art
Generally, an LCD includes a pair of panels each having electrodes formed on the inner surface, and a dielectric anisotropy liquid crystal (LC) layer interposed between the panels. Two polarizers are separately attached to the outer surfaces of the panels. In the LCD, a variation in the strength of an electric field generated by the electrodes changes the orientations of LC molecules in the LC layer, and the orientations of the LC molecules determine the polarization of light passing through the LC layer. At this time, the polarizers either pass or block the polarized light to produce white (or clear) or black (or dark) regions. As a result, a desired image display is realized.
LCDs are non-emissive displays and they do not produce any form of light. Accordingly, the LCDs utilize artificial light emitted from lamps of a backlight unit separately provided, or ambient light, as a light source.
Depending on kinds of the light source used for the image display, the LCDs are divided into three types: transmissive, reflective, and transflective (transmissive-reflective). In transmissive LCDs, the pixels are illuminated from behind using a backlight. In reflective LCDs, the pixels are illuminated from the front using incident light originating from the ambient environment. Transflective LCDs combine transmissive and reflective characteristics. Under medium light conditions, such as an indoor environment, or under complete darkness conditions, these LCDs are operated in a transmissive mode, while under very bright conditions, such as an outdoor environment, they are operated in a reflective mode. The reflective and transflective LCDs are commonly used in small and medium size display devices.
In a transflective LCD, there are transmission areas and reflection areas. In the reflection areas exterior light passes through color filters twice because of reflection, while in the transmission areas light emitted from the backlight that is provided behind an LCD panel assembly passes through the color filter only once. Due to these characteristics, the difference of color tone between the transmission areas and the reflection areas may occur.
There are two commonly used methods to solve the above-mentioned problem. The first method is to form the color filters of the transmission areas more thickly than the color filters of the reflection areas. The second method is to form light holes in the color filters of the reflection areas.
However, the latter method has some drawbacks. In this method, after the formation of the holes, an overcoat layer is coated on all the color filters in order to compensate a step difference between the color filters with the holes and the color filters without the holes and thus to create a planarized surface. In this case, however, perfect planarization is technically impossible. Accordingly, even if the overcoat layer is formed on all the color filters, a cell gap at the reflection area with the holes and a cell gap at the transmission area without the holes are different from each other. Also, the common electrode is depressed in the vicinities of the holes. Accordingly, the orientations of the LC molecules become poor and those molecules may be abnormally operated.